Hand Tools Archive
I was in band in school, too. We had sub-freezing field shows, but I think there's so much outdoor ambient noise and echo that it's a little easier to get away with bad tuning.
We never tuned other than individually except for concerts, but even then, temperature changes tuning.
On guitars, the problem is compounded as it would be for a violinist. When your fingers are stiff, they don't move as far as fast and it's almost like a separate skill to learn to play things that are otherwise fluid when your fingers are cold. I couldn't ever do it (the only time I ever played for pay was high school).
I think our school marching band strategy when we were out of tune in a field show was just to play louder. The nuances of the trombone escape me - I'm sure your positions are already baked permanently into your brain, but the rest of us would say "move the slide a little to make up for it "